1. Field of the Invention
The invention lies in the field of packaging technology and relates to a method and to a device. The method and device serve for packaging flat objects, for example individual printed products, from stack-like groups of printed products or from stack-like groups of printed products and other flat objects, such as for example CDs, flat pattern objects or flat pattern bags.
2. Description of Related Art
It is known to package flat objects of the above mentioned type with the help of a quasi endless packaging material web (e.g. plastic film or paper web supplied from the roll). Thereby, such a packaging material web is applied around the objects which are conveyed one after the other and distanced to one another, or a packaging material web is fed to such a row on both sides. The packaging material web (or webs) in the longitudinal direction on the upper side of the row or laterally thereto is closed in longitudinal seams, and in transverse seams between, in each case, two successive objects transversely to the longitudinal direction. As the case may be, the objects which are enclosed on all sides by packaging material are separated from one another directly after the creation of the transverse seams or also simultaneously with this.
With the application of plastic film as a packaging material, the longitudinal and transverse seams are usually created by way of welding, wherein the separation of the packaged objects may be carried out simultaneously with the creation of the transverse seams. With the application of paper as a packaging material, an adhesive, activatable by heat, may be deposited onto the packaging material directly before the feeding of the packaging material web to the row of objects to be packed, at the locations of the longitudinal and transverse seams, so that the seams may then be created with means which are similar as is the case with welded seams on plastic packaging. It is possible to close the seams by way of embossing or by way of other known methods which are matched to the applied packaging material.
For such processing operations such as welding, bonding etc. . . . , the printed products are conveyed in streams into a processing station and conveyed out of this again. The processing station is advantageously designed in a manner such that the conveying of the packaged objects does not need to be interrupted for the processing, but is able to be continuously operated. This means that processing tools which are to act on the printed products to be packaged over a defined time, must also be conveyed with the stream of conveyed objects to be processed during this time, and in a manner such that they have no relative speed with respect to the printed product, at least in the conveying direction. The material layers to be connected must simultaneously be located in a defined position to one another, before and during the processing or connection, so that a connection or seam may be achieved without any faults.
A processing device is moved in an intermittent manner according to EP 0712 782 A1. The processing device consists of a welding and separating device with a welding beam and a counter-beam in the transverse direction of a stream of conveyed objects, as well as deflection rollers which lead a conveyor belt around the deflection rollers. The processing device has the same speed and movement direction as the stream of conveyed objects in a first phase of the movement beginning in a start position, and the processing takes place by way of welding and separating a packaging tape. In a second phase, the processing device moves back against the stream of conveyed objects to the start position, and is opened, so that the stream of conveyed objects is not affected. The intermittent movement necessitates a corresponding control effort, an energy expense and a loading of the material, corresponding to the constant alternating loading of the moved parts. It is particularly the cycle speed of the device which is limited on account of the intermittent movement. In the case that the objects to be packaged are relatively thick, with greater belt tensions, a correspondingly larger gap is present between the upper and the lower packaging layer, and for example, a welding may not be carried out in a reliable manner. If the belt tension is lower, then the packaging material, as the case may be, lies in a loose manner between the objects, and its arrangement may no longer be controlled, in particular at higher speeds, which may likewise lead to poor connections.
A packaging device is disclosed in DE 26 51 131 A1 with which two welding jaws fastened in each case on a shaft are arranged in the transverse direction on both sides of a conveyor path. The welding jaws are not directed to the conveyor path in the idle position. For welding, the welding jaws are rotated counter to one another, press against a packaging bag from both sides, and rotate further away from one another. This, in each case, is effected in an intermittent and jerky manner, synchronized with the position of the objects to be packaged. Here too, in principle, the same stresses and limitations occur on account of the intermittent movement. The problem of the unclear position of the packaging material also remains the same.
A rotating processing drum is suggested in WO 2004 018 297, in order to achieve a uniform, i.e. non-intermittent movement of processing tools. The stream of conveyed objects runs around this drum, and thereby the drum is wrapped by a pressing tape which presses the stream of conveyed objects against the tools, in order, for example, to permit a welding. Although the position of the packaging material is defined by way of this, however a complication of the device results due to the wrapping of the drum by the stream of conveyed objects. The stream of conveyed objects, after the deflection around the processing drum as a rule needs to be deflected back again into the initial direction. Additional belts rollers and drives are required for this, and the space requirement for the complete device is increased.
It is therefore the object of the invention to provide a method and a device for packaging flat objects of the initially mentioned type, which overcomes the disadvantages discussed above.